Articular cartilage defects have long been a serious problem for patients and orthopedic surgeons. No matter how small the initial defect, it carries with it a high potential for progressing into larger, more symptomatic defects, with the accompanying early arthritis and disabling pain and dysfunction.
Over the years, a number of different procedures have been devised for treating articular cartilage defects.
Articular cartilage defects have traditionally been treated with chondroplasty, shaving, microfracture, abrasion arthroplasty and, most recently, autologous transplantation. Early on, the treatment of articular cartilage defects was principally concerned with preventing a progression of the defect. More recently, attention has been focused on developing ways to actually repair the defect and effect articular cartilage healing.
More particularly, chondroplasty and shaving are principally concerned with removing offending portions of the articular cartilage (e.g., loose flaps, rough edges, etc.) so as to prevent the enlargement of an existing articular cartilage defect. While chondroplasty and shaving have proven helpful in preventing the spread of an existing articular cartilage defect, they do not actually repair the defect or effect articular cartilage healing.
The basic idea behind microfracture and abrasion arthroplasty is to violate the subchondral plate, thereby allowing blood (preferably including marrow cells) to fill the defect and initiate an injury repair. This may be done in a variety of ways well known in the art, e.g., with a rasp to abrade the defect, a pick to pick away the area of the defect, a drill to microdrill the area of the defect, an RF probe (or otherwise) to heat and thereby disrupt the region of the defect, etc. It is known that such a procedure does not actually cause articular cartilage to grow in the defect. Rather, a fibrocartilage/Hyaline cartilage regenerates which, while generally not as good as articular cartilage since it lacks the mechanical properties of the articular cartilage, is certainly better than bare bone. However, a common problem with this technique is that the blood (and marrow) cells do not tend to stay seeded in the defect, since they are commonly wiped away by joint motion and/or other factors.
Autologous cartilage transplant is a potentially attractive alternative for healing articular cartilage defects. This has principally been addressed in two different procedures.
In one procedure, generally referred to as osteocondral grafting, a plug of healthy articular cartilage and underlying bone is harvested from a donor site and transplanted to the defect site. While this technique has proven effective, it typically causes serious damage to the donor site. In addition, it can be difficult to find donor sites with the proper surface profiles, and it can be difficult to properly align the layers (i.e., cartilage and underlying bone) of the graft plug with the layers of the defect site.
In the second procedure, sometimes referred to as autologous cell transplantation, cells from healthy articular cartilage are harvested, multiplied outside the body and then reimplanted at the defect site. This has been accomplished most recently by a system available from Genzyme of Boston, Mass. under the trade name Carticell. However, this system does have its drawbacks: it requires at least two surgical procedures (i.e., one to harvest the cells and one to reimplant them); it is relatively expensive; and there are limits in the size of lesion, and the number of lesions, that can be treated. Also, with this system, the defect generally has to be “contained” in order for the system to be successful.